Sad but truth - bitcoin indeed is centralized system that pretends it wants to be decentralized.

1. The blockchain split incident. It required central authority to split the chain. It required central authority to cause the problem in the first place (which was formed by accumulating >50% hash power).

2. The client code is controlled by central authority. Does anyone check the source code and compile it by hand before using it? Even if someone does, 99% of userbase just installs whatever they get each time a new version is released. If that code is secretly controlled by some authority, they have all the power they need and you can't do anything about it.